Heat and light reflecting spandrel

ABSTRACT

Durable glass spandrels are provided with transparent light and heat reflective coatings on the inwardly glazed glass surface and with substantially opaque ceramic enamel coatings adhered to the transparent light and heat reflective coatings. The spandrels are light and heat reflecting and provide for aesthetically matched vision and spandrel areas in curtainwall construction by utilizing a ceramic enamel coating which reflects light in the same spectral region of light transmitted by the transparent coating and glass combination.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Pat. application Ser.No. 291,430 filed on Sept. 22, 1972, now U.S. Pat. No. 3,869,198, in thename of John D. Ballentine and entitled "Heat and Light ReflectingSpandrel."

BACKGROUND OF THE INVENTION

This invention relates to light and heat reflecting glazing units. Thesearchitectural glazing units are particularly suited for installation inthe spandrel areas of curtainwall construction.

A spandrel area, as the term is used herein, refers to the opaque area,as contrasted to the vision area of a curtainwall, which is formed bythe use of spandrel panels which are either intrinsically opaque or arerendered opaque by various backing or coating materials. Spandrel panelsare designed to thermally isolate and conceal certain portions of theexterior structure of a building, as well as conceal interiorly locatedbuilding fixtures. Thus, spandrel panels or spandrels are frequentlyemployed to conceal floor slabs, the vertical span between floors andceilings or between successive viewing closures, heating and airconditioning convectors and the like. Spandrel panels are principallyemployed to conceal those portions of a building that would not beaesthetically pleasing if capable of being viewed from the exterior of abuilding. However, spandrel panels also find use in building zones whereit is desired to maintain a degree of privacy, such as at the groundlevel of a building.

In the past, various attempts have been directed toward producingspandrel panels that closely match or pleasingly contrast in color andreflectivity with adjacent, transparent glass panels in the viewing orvision areas of a building.

With the development of highly reflective transparent metal and metaloxide coatings, it has been an objective to develop spandrel panelswhich would match or harmonize with the coated glass vision panels to beglazed adjacent to spandrel panels. Because the back lighting conditionsdiffer greatly from occupied spaces behind vision panels and servicespaces or structural spaces behind spandrel panels, it has beendifficult in the past to find spandrel panel combinations which couldprovide this matching or harmonizing appearance.

SUMMARY OF THE INVENTION

This invention relates to an article, e.g., a spandrel panel forreflecting visible light. The article includes a transparent substratehaving a first major surface and a second major surface opposite to thefirst major surface. A transparent reflective coating is disposed oversubstantially all of the first major surface of the substrate. Thetransparent reflective coating has (1) a transmitted dominant wavelengthfor visible light which is determined by transmittance to visible lightof the substrate and the transparent, reflective coating and (2) areflectance to visible light which is determined by the transparentreflective coating and the second surface of the substrate. An opaque,reflective coating is disposed over substantially all of the transparentreflective coating. The opaque, reflective coating has a reflectivedominant wavelength of visible light substantially equivalent to thetransmitted dominant wavelength to provide the article with a totalreflectance to visible light. The total reflectance to visible light ofthe opaque coating exceeds the visible light reflected from (1) thetransparent, reflective coating and (2) the second surface of thesubstrate. Further, the opaque coating has a dominant wavelengthsubstantially equivalent to the dominant wavelength of light transmittedthrough the transparent reflective coating and the substrate.

This invention also relates to a curtainwall for a structure using thecombination of vision panels and spandrel panels to provide a colorharmonizing appearance to the eye under external lighted conditions.

The opaque coating is selected to have a reflective dominant wavelengthsubstantially the same as the dominant wavelength, characterizing thelight transmission of a combination of the transparent, reflectingcoating and the transparent substrate. Preferably, the opaque coatinghas an excitation purity exceeding that for the transmission of thetransparent, reflecting coating in combination with the substrate. Thisgreater saturation or purity of color for the opaque coating isparticularly important for spandrels in buildings so glazed that theinterior lighting is from transmitted outdoor light.

The transparent, reflecting coating may be a metal or metal oxidecoating or may be a combination of films to produce interference colors.If the coating is metallic and subject to oxidation if exposed it ispreferably overcoated with a protective coating of silica or the like.Although conventional metal coatings are suitable, metal oxide coatingsare preferable because of their inherent durability. Any transparent,reflective, metal oxide coating suitable for use in vision area glazingmay be employed.

The metal oxide coatings preferred in the present invention include theoxides of tin, chromium, titanium, iron, silica, aluminum, nickel, lead,copper, zinc, vanadium, tungsten, tantalum and cobalt. The mostpreferred metal oxide coatings comprise the oxides of cobalt, chromiumand iorn. Coatings comprised of mixtures of oxides of two or more metalsare also preferred. The preferred oxides have been found to besufficiently durable for outside glazing and are efficiently depositedby known methods as described below.

The preferred transparent substrates are glasses, with commonsoda-lime-silica glasses particularly preferred. Clear or tinted glassesmay be employed. For example heat absorbing glasses, such as those soldunder the trademarks, SOLEX, SOLARGRAY and SOLARBRONZE may be used.Examples of such glasses are set forth in U.S. Pat. Nos. 3,296,004 andRe. 25,312 to Duncan and to Duncan et al.

The opaque coating is preferably a ceramic enamel which is durable andcan withstand abrasion during installation and temperature changes inuse without scratching or spalling. Glass frit enamels, for example leadborosilicate glass frit enamels, may be used effectively.

It is desirable for the frit or enamel to have a coefficient ofexpansion less than the glass substrate because this difference inexpansion results in the enamel being in a state of compression uponcooling of the coated article from the enamel firing temperature to roomtemperature. A more durable article results when the enamel is in astate of compression.

Alumina, silica, boric oxide, lead oxide, potassia, and soda are typicalconstituents in the glass enamels employed in preparing the articles ofthis invention. Other materials may also be present as constituents inthe glass enamels employed. Some of these other constituents may includecalcium oxide, barium oxide, zinc oxide, magnesium oxide, strontiumoxide and the like as materials which contribute to the physicalproperties of the ceramic enamel. Other ingredients may also be presentto impart color to the ceramic enamel and to act as opacifiers. Suchmaterials include titanium dioxide, cobalt oxide, the oxides ofmanganese, chromium copper oxide, iron chromate, potassia dichromate,lead chromite and the like.

Various methods may be employed for producing the metal oxide coatingsof the present invention. Methods for preparing tin oxide films includethe methods described in U.S. Pat. Nos. 2,566,346; 3,107,177; 3,185,586and the like. Iron, cobalt, chromium and other metals of groups IV, V,VI, VII, and VIII are preferably applied by pyrolization techniques asdisclosed in U.S. Pat. Nos. 3,202,054; 3,081,200 and 3,660,061. Othertechniques such as vacuum deposition and cathodic sputtering may also beemployed to produce metal oxide films for the articles of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a portion of curtainwallshowing a vision area glazing panel in combination with a spandrel paneljoined by a frame member mounted onto a floor supporting structure;

FIG. 2 is a chromaticity diagram showing the significant colorcharacteristics of the spandrel and vision panel comprising thepreferred curtainwall according to this invention; and

FIG. 3 is a schematic cross-sectional view of a portion of a curtainwallshowing a vision area glazing panel in combination with a spandrelpanel, incorporating features of the invention, joined by a frame membermounted onto a floor supporting structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a curtainwall comprises spandrel area panels, 1,and vision area panels, 2, mounted in a frame member, 3. The framemember, 3, is connected to a mounting, 4, which is mounted on astructural member, 5. A floor, 6, which is mounted on structural member,5, faces the wall area of the frame, 3, and spandrel panel, 1, so thatthe edge of the floor, 6, the structural member, 5, the mounting, 4, andany material below floor level and above the next lower ceiling arehidden from exterior view by the spandrel panel, 1, and the frame, 3.

The spandrel panel, 1, comprises a transparent substrate, 7, which ispreferably a durable refractory material. Most preferably the substrateis glass. On the substrate, 7, are two coatings. Disposed on theexterior, outward facing surface is a transparent, reflective coating,8, and on the inward facing surface is an opaque, reflective coating, 9.

The vision panel, 2, comprises a transparent substrate, 10, which ispreferably a durable refractory material. Most preferably the substrateis glass. Disposed on the exterior outwardly facing surface of thesubstrate, 10, is a transparent, reflective coating, 11. As inconventional glazing, the frame is provided with weep holes, 12, and adrain space, 13.

Coating, 11, of the vision panel, 2, and coating, 8, of the spandrelpanel, 1, are substantially identical. The mere use of identicalexterior coatings for the vision panel, 2, and the spandrel panel, 1,does not result in a matching or harmonizing appearance for differingback-lighting prevails in the spandrel and vision areas. The opaquecoating, 9, on the spandrel panel, 1, has a reflectivity such that itreflects 15 to 50 percent of incident visible light, 20 to 80 percent ofincident infrared energy and preferably at least 35 percent infraredenergy. Higher infrared reflectance is desirable to prevent heat buildupin the spandrel areas with consequent air conditioning overloads oroccasional glass fracture.

The opaque coating, 9, is found to effectively give the spandrel panel,1, an appearance closely matching that of a vision panel, 2, backed by alighted space if the color of the opaque coating is such that itsreflective dominant wavelength is substantially the same as that oflight transmitted through the corresponding vision panel, 2.

This may be seen with reference to FIG. 2, in combination with FIG. 1.An outdoor ray of light 14 strikes the transparent, reflective coating,11, of vision panel, 2. A portion of light, 15, is reflected back towardthe outdoors from the coating, 11. A portion of light, 16, istransmitted through the coating, 11, and substrate, 10. It is thisportion of light, 16, which is characterized as having the transmitteddominant wavelength representing the substrate, 10, in combination withthe transparent, reflective coating, 11.

A third portion of light, 17, is reflected from the back surface of thesubstrate, 10, and is directed outwardly through the coating, 11.Continued internal reflections occur, but their effect is negligible forthe purpose of understanding the invention.

The total light reflected, portions 15 and 17, is from about 25 to about45 percent of the incident light, 14. This is the luminous or visiblereflectivity of the coated surface of the vision panel.

With some light behind the vision panel, 2, in the interior of abuilding there is light, 18, incident on the interior surface of thesubstrate, 10. A portion of this light, 19, is reflected from the coatedsurface and a portion, 20, is transmitted mixing with external reflectedlight 15 and 17. Portions of interior light (not shown) also arereflected internally and from the uncoated surface of the substrate, 10.

In FIG. 2, the color apparent for reflection from the transparentreflective coating side of a glass substrate is indicated by thenumerals 15, 17 and 20 corresponding to the reflection rays 15 and 17and transmitted light, 20 of FIG. 1. The particular coating andsubstrate illustrated are those of the first example which follows. Thetransmitted light is indicated by the numeral, 16, corresponding to thetransmitted ray, 16 of FIG. 1.

Referring again to FIG. 1, light 14, striking the spandrel panel is bothreflected from the coating, 8, as reflected light, 21, and transmittedto the opaque coating, 9, and reflected from it as light, 22. Againinternal reflections are ignored. In FIG. 2, the mixture of reflectedlight 21 and 22 is indicated by numerals 21 and 22. From about 30 to 50percent of incident light, 20, is reflected as reflected light 21 and 22from the spandrel panel. In general, the light reflected from thespandrel panel is about 2 to 10 percent greater than the light reflectedfrom the corresponding vision panel.

Although no light is incident on the opaque coating, 9, when thespandrel panel, 1, is installed in a wall, the reflectivity of thecoating, 9, at its surface adjacent the substrate, 7, may be consideredas being the same as that for the exposed surface facing the structure.Thus, the internal surface reflectivity is determined by measuring thereflectivity of the opaque coating exposed before installation. Thedominant wavelength characterizing the coating, i.e., 579 nanometers, issubstantially that for the transmitted light of the vision panel, i.e.,579 nanometers, and is represented by the numeral, 9, in FIG. 2.

The excitation purity of the opaque coating is observed to be greaterthan that for the transmitted light of the vision panel. This ispreferred for it results in matching the vision panel with the spandrelpanel over a greater range of indoor and outdoor lighting conditionsthan when the excitation purity of the opaque coating is of the order of10 percent or less. Nevertheless, opaque coatings of less excitationpurity are useful so long as their characteristic dominant wavelength iswithin about ±5 to ±10 nanometers of the transmission dominantwavelength of the corresponding vision panel.

The present invention may be more fully understood from the followingexample. This example describes a preferred embodiment which isaesthetically pleasing, durable and highly efficient as a heat screenfor air conditioned buildings.

EXAMPLE I

Commercial float glass is produced having a typical X-ray diffractionanalysis as follows:

                       PARTS BY WEIGHT                                            COMPONENT          (Or Percent by Weight)                                     ______________________________________                                        SiO.sub.2          73.0                                                       Na.sub.2 O         13.7                                                       K.sub.2 O          0.68                                                       CaO                8.9                                                        MgO                3.85                                                       Al.sub.2 O.sub.3   0.11                                                       SO.sub.3           0.37                                                       Fe.sub.2 O.sub.3   0.128                                                      ______________________________________                                    

As the glass is being manufactured to a thickness of 0.25 inch, its topsurface is coated according to the method of U.S. Pat. No. 3,660,061 toDonley et al.

Between the float bath and the lehr the ribbon of hot glass (1000° to1100° F.) is contacted with a spray of coating solution.

The solution comprises on a 20 gallon solvent basis the following:

    Methylene chloride       221.8 pounds                                         Cobalt Acetylacetonate   24.8 pounds                                          Iron Acetylacetonate     3.22 pounds                                          Chromium Acetylacetonate 8.38 pounds                                      

The resulting coated glass has the following characteristics when viewedtoward the coated surface: Luminous or visible reflectance, 34 percent;total solar ultraviolet reflectance, 26 percent; total solar infraredreflectance, 23 percent; total solar energy reflectance, 29 percent;dominant wavelength, 560 nanometers; excitation purity, 4 percent;chromaticity coordinate x 0.313 and y 0.329.

The coated glass has the following characteristics when viewed towardits uncoated surface: Luminous or visible reflectance, 27 percent;dominant wavelength, 550 nanometers; excitation purity, 4 percent;chromaticity coordinates x0.310 and y0.333.

The coated glass transmission of light is characterized as follows:Luminous or visible light transmitted, 39 percent; total solar energytransmitted, 44 percent; dominant wavelength, 579 nanometers (see point16 in FIG. 2); excitation purity, 12 percent; chromaticity coordinates x0.334 and y 0.338.

Pieces of this coated glass are cut to proper size for vision panels andspandrel panels in curtainwall construction. Those panels for spandrelpanels are further processed.

An enamel is applied uniformly over the uncoated or coated surface ofthe glass pieces for spandrel use. An olive-green to tan appearingceramic enamel (Drakenfield, EG 10094) is applied to the glass. Theenamel frit is analyzed on a dry basis by conventional wet chemicaltechniques and by conventional absorption spectrophotometric techniqueswith the following results.

    ______________________________________                                        Wet Chemical Analysis of Dried Frit                                           ______________________________________                                        SiO.sub.2           28.60                                                     Na.sub.2 O          2.36                                                      K.sub.2 O           .08                                                       CaO                 Trace                                                     MgO                 Trace                                                     BaO                 .13                                                       PbO                 50.55                                                     Al.sub.2 O.sub.3    .76                                                       ZrO.sub.2           1.26                                                      ZnO                 .46                                                       B.sub.2 O.sub.3     3.67                                                      SO.sub.3            .56                                                       Sb.sub.2 O.sub.5    None                                                      Ign. Loss           3.24                                                      Absorption Spectrophotometric Analysis                                        Fe.sub.2 O.sub.3    .18                                                       TiO.sub.2           7.41                                                      CoO                 .08                                                       NiO                 .01                                                       Cr.sub.2 O.sub.3    .27                                                                           99.62                                                     ______________________________________                                    

The glass is heated in a muffle furnace for 8 minutes at 1150° F. Thearticle is then cooled to room temperature at a sufficient rate toimpart some temper to the coated glass.

The resulting spandrel panel is examined. Viewed toward the transparent,reflective film the article has the following characteristics: Luminousor visible reflectance, 37 percent; total solar ultraviolet reflectance,29.6 percent; total solar infrared reflectance, 29.8 percent; totalsolar energy reflectance, 33 percent; dominant wavelength, 566.8nanometers; excitation purity, 5.9 percent; chromaticity coordinates x0.317 and y 0.332.

The character of the opaque coating is observed by viewing the articletoward that coating. It is characterized as follows: Luminous or visiblereflectance, 28.8 percent; total solar ultraviolet reflectance, 9.2percent; total solar infrared reflectance, 42.2 percent; total solarenergy reflectance 33.9 percent; dominant wavelength, 579.6 nanometers;excitation purity, 31.1 percent; chromaticity coordinates x 0.372 and y0.370.

The spandrel panel is opaque to the unaided eye and has the followingproperties viewed in transmission: Luminous or visible transmittance 0.7percent; total solar untraviolet transmittance, 0.2 percent; total solarinfrared transmittance, 10.4 percent; and total solar energytransmittance, 5.1 percent.

Vision panels and spandrel panels are mounted in frame members to form acurtainwall about a supporting structure. The interior of the structurefaced by spandrel panels is backed by structural members, floors,ceilings and the like and is dark. The interior of the structure facedby vision panels is open and is lighted by transmitted exterior light.The curtainwall structure is viewed under a variety of outdoor lightingconditions. In particular, observations are made under the followingconditions: bright, full sunlight with sharply defined shadows; sunlightwith haze and poorly defined shadows; bright sunlight with clouds andindistinct shadows; cloudy sky with no apparent sun and no shadows;morning, full sunlight and evening, full sunlight. Under all theseconditions the vision panels and spandrel panels match or harmonizesufficiently so that, to the human eye, the entire curtainwall appearsuniform in color.

The quantitative characterization of the panels comprising thecurtainwall of this example are determined using a conventionalspectrophotometer, such as a Beckman DK-2A spectrophotometer, with astandard illuminant "C" and with magnesium carbonate as a standard whitereflector. All transmittance, reflectance and color information ispresented according to the conventions of the International Commissionon Illumination (C.I.E. system) as discussed in Hardy, Handbook ofColormetry.

The following example demonstrates the applicability of the principlesof this invention using another glass composition and comprises anotherembodiment of this invention.

EXAMPLE II

Bronze colored glass is float formed and coated with a coatingcomposition like that employed in Example I. The glass composition isthat described in U.S. Pat. No. 3,296,004.

The coated glass has the following transmittance characteristics:luminous or visible transmittance, 22 percent; dominant wavelength, 582nanometers; excitation purity, 20 percent.

Pieces of this glass are cut to proper size for vision panels andspandrel panels in curtainwall construction. Those panels for use asspandrel panels are further processed.

An enamel is applied uniformly over the uncoated surface of the glasspieces for spandrel use. The enamel employed is Drakenfield 10100 whichhas an olive appearance. The glass is heated in a muffle furnace for 8minutes at 1150° F. The article is then cooled to room temperature.

The resulting spandrel is examined. The opaque coating has a luminoustransmittance of about 27 percent, a dominant wavelength of about 577nanometers and an excitation purity of about 30 percent. In reflectionthe vision panels and spandrel panels harmonize over a wide range oflighting conditions. The particular specimen examined appears to matchthe vision panel best when the space behind the vision panels isdarkened.

Several more specimens are prepared using a variety of enamels. Thoseenamels having reflectance characteristics within the following rangesprovide spandrel panels which closely match or harmozine with the visionpanels comprising coated, bronze heat absorbing glass: luminous orvisible reflectance, 10 to 50 percent; dominant wavelength 570 to 590nanometers; excitation purity, 10 to 40 percent.

Referring to FIG. 3, there is shown a curtainwall embodying principlesof the instant invention.

The vision area panel 2 is replaced with a vision area panel 30 havingthe coating 11 on the inwardly facing surface of the substrate 10. Thespandrel area panel 1 of FIG. 1 is replaced with spandrel area panel 32.The spandrel area panel 32 has the transparent, reflective coating 8 onthe inwardly facing surface of the transparent substrate 7. The opaque,reflective coating 9 is advantageously provided over the inwardly facingsurface of the coating 8 as shown in FIG. 3.

The principles of this invention may be employed to prepare spandrels orother coated panels which have the coatings arranged in a mannerdifferent from that of the preferred embodiments. So long as thetransmittance characteristics of a transparent reflective coating visionpanel are employed to dictate the reflectance characteristics of anopaque backing in accordance with the required relationships of thisinvention, harmonizing panels may be produced. For example, an opaquepanel could be employed with an opaque coating disposed over it and amatching transparent, reflective coating over the opaque coating. Inthis instance the reflectance of the opaque coating would have adominant wavelength substantially the same as the transmitted dominantwavelength for the transparent reflective coating alone.

Also, the coatings may be on either surface of transparent substrates solong as the outwardly facing reflectance is controlled by the coatingrelationships and orders established in accordance with this invention.

It will be understood from this disclosure and from the claims that thepresent invention is not limited to particular materials nor to theparticular embodiments now preferred and described here to illustratethis invention. Accordingly, the present invention embraces equivalentembodiments which will become apparent to those skilled in the art fromthis disclosure and which are embraced by the following claims.

What Is Claimed Is:
 1. An article for reflecting visible lightcomprising:a transparent substrate having a first major surface and asecond major surface opposite to the first major surface; a transparent,reflective coating disposed over substantially all of the first majorsurface of said substrate, said transparent reflective coating having(1) a transmitted dominant wavelength for visible light, whichtransmitted dominant wavelength is determined by transmittance tovisible light of said substrate and said transparent, reflective coatingand (2) a reflectance to visible light which is determined by saidtransparent reflective coating and the second surface of said substrate;and an opaque, reflective coating disposed over substantially all ofsaid transparent, reflective coating, said opaque, reflective coatinghaving a reflective dominant wavelength for visible light substantiallyequivalent to the transmitted dominant wavelength to provide the articlewith a total reflectance to visible light that exceeds the visible lightreflected from (1) said transparent reflective coating and (2) thesecond surface of said substrate and to provide the article with adominant wavelength substantially equivalent to the dominant wavelengthof light transmitted through said transparent reflective coating andsaid substrate.
 2. A curtainwall for a structure, the curtainwallcomprising in closely spaced relation, vision panels and spandrelpanels, the combination having a color harmonizing appearance to the eveunder external lighted conditions comprising:vision panels wherein eachof said vision panels comprises: a transparent substrate having aninwardly facing surface facing the interior of the structure and anoutwardly facing surface opposite to the inwardly facing surface; and atransparent reflective coating of substantially uniform transparencythroughout disposed over substantially all of the inwardly facingsurface of said transparent substrate, said transparent, reflectivecoating in combination with said transparent substrate providing each ofsaid vision panels with a transmitted dominant wavelength; and spandrelpanels wherein each of said spandrel panels comprises: a transparentsubstrate having an inwardly facing surface facing the interior of thestructure and an outwardly facing surface opposite to the inwardlyfacing surface; a transparent reflective coating substantially identicalto that of said vision panel disposed over substantially all of saidinwardly facing surface of said transparent substrate of said spandrel;and an opaque, reflective coating disposed over substantially all of thesurface of said last-mentioned transparent reflective coating, saidopaque, reflective coating having a reflective dominant wavelengthsubstantially equivalent to the transmitted dominant wavelength of saidvision panels.